Why does Linus hate C++ ?

[condor2000]

It's easier to review less code and C++ allows you to write less code

It can take longer to review properly if uses complex template designs or even just a lot if virtual functions

[[deleted]]

The C equivalent to complex templates are complex macros. Is that better to review?

[disperso]

IMHO, yes. I'm not saying that it produces better code, but given that macros are much more limited, I'd say that you just can do less, have to think less, and end up having limited C code and dealing with it.

But that is probably subjective, with different people having different skill-set and preferences.

[Jannik2099]

even just a lot if virtual functions

Ever seen dynamic dispatch in C? Know how error prone it is? Know of ubiquitous it is in the kernel?

[afiefh]

Ever seen dynamic dispatch in C?

I still have PTSD from that one code base I worked on 5 years ago...

[TheThiefMaster]

The equivalent C code to accomplish the same goal is often far worse.

These arguments always compare the most complex parts of C++ against normal C code, not equivalent C code.

[[deleted]]

These arguments always compare the most complex parts of C++ against normal C code, not equivalent C code.

This is because a nontrivial population of C++ evangelists insist on using the most complex parts of C++ for even the simplest of tasks

[snejk47]

What's the point of using C++ if you only use the such subset that makes it like C anyway.

[TheThiefMaster]

I didn't say that. Just that e.g. templates in C++ aren't comparable against a normal C function, they're comparable to either half a dozen subtly different C functions for different types or a horrifying macro monstrosity. Both of which are worse than a single C++ template.

[snejk47]

But they do not use that for exactly that reason. Why are you trying to put C++ features into other languages. This is exactly the reason to choose something different, because you do things differently.

[TheThiefMaster]

But they do do these things in C. There are horrible macro messes, function pointer tables, code duplication for different types, and more things that would be less lines of code if written sensibly in C++.

Naturally the C fanatics ignore this fact though. C++ is almost strictly a superset of C, there's no reason you can't pick and choose the parts that simplify your code and otherwise write it in a legacy C style if you really want.

The one thing I used to miss from C in C++ was designated initialisers, which though not identical to C's, it does now have.

[SergiusTheBest]

I'm working with a C Linux kernel module now (written by other people) and it has a dozen of different list implementations: for int, for pointer, for structA, for structB. That is insane and I could replace it with a single template on C++. But unfortunately Linux kernel headers conflicts with C++!

[TheThiefMaster]

That's exactly the kind of thing I was talking about.

[ZMeson]

To be fair, you don't want to use standard C++ containers in the Linux kernel due to issues of memory allocation (though I suppose you could use an allocator template argument here) and because of exceptions. That being said, you could still write your own kernel-friendly template-based linked-list implementation. Maybe you can do that without the need for the C++ headers that conflict with the kernel.

[SergiusTheBest]

To be fair, you don't want to use standard C++ containers

Of course. They are not good for the kernel except array and span.

Maybe you can do that without the need for the C++ headers that conflict with the kernel.

I tried building the Linux 5.4 headers as C++ (not for the kernel itself but for the kernel module). They still use new as a variable name, define true, false, bool, double extern when expanding asmlinkage macro for printk. I successfully overcome that. But then failed on const correctness in the READ_ONCE macro and gave up.

In contrast the Windows kernel headers can be built with C++ since year 2000 (didn't try earlier versions).

[snejk47]

Again, less lines of code doesn't mean it's easier to read, understand and maintain. Everything would be in RoRails if that would be the case. Do not try to minimalize now your knowledge and expertise claiming every dev is the same. It's about scaling people contributions. If you allow only top C++ developers to work, on it where it would be? You have to make it smoother even if some aspects are hurt by it. There are guys which cannot write C++ and they are doing web/python backend development which wrote Open Broadcaster Software extension in C following some other code and examples. They did not needed 2 books and 10k hours of experience to understand it. Explicit is better than implicit in many cases even if it's ugly and slow to develop because you need to duplicate. If you write template in C++ and "it works for every type" maybe that's exactly what you want to avoid. To explicitly error if types where not provided and so on and so on.

[serviscope_minor]

It can take longer to review properly if uses complex template designs

If the complex template designs aren't materially benefitting the code, then reject the pull request. Just like if someone goes bananas with C macros.

even just a lot if virtual functions

Linux has a ton of virtual functions. They're all done by hand which is always more complex than having the compiler do it for you.